(1) Field of the Invention
The present invention relates to an accumulator for storing strip material received from a supply coil prior to being fed to strip processing equipment utilized to form the strip into a continuous tube or pipe. More specifically, it is known that many industrial processing lines utilize an input material which is delivered from a supply coil. Such equipment typically utilize a strip material, such as a metallic strip material, as an input and require that the strip is fed continuously. The strip is available from a coil which is payed out until depleted. In order to avoid the stopping of the processing of the line upon the depletion of a supply coil, various strip accumulators have been developed which receive strip from the input or supply coil and store a certain amount thereof while paying out strip to the processing line. These accumulators permit the processing line to remain active during the time the new input strip coil is attached, by welding to the end of the coil which has been depleted.
(2) Description of the Prior Art
The present invention is directed to improvements in the type of strip accumulating system disclosed in U.S. Pat. No. 3,782,662 dated Jan. 1, 1974 entitled SIMPLIFIED STRIP ACCUMULATION, for example,
In accordance with the teachings of the above prior art, the strip to be coiled is supported on a horizontally disposed table surrounding a circular cage of rollers around which the inner set of convolutions is formed. The strip material is fed onto the table by means of a set of driven feed rolls or pinch rolls which advance the strip onto the table at the desired rate of speed. The table is in the nature of a turntable adapted to rotate around the inner arbor. The rotary table will be provided with a set of radially disposed idler rolls adapted to underlie the inner set of convolutions, i.e., the set of convolutions built-up against the inner arbor, thereby permitting the inner set of convolutions to be rotated independent of table rotation when strip is being withdrawn from the accumulator. In this connection, the strip is withdrawn from the device either by means of driven exit rolls or by tension exerted by the processing line or the like to which the accumulated strip is being delivered. While other drive means may be employed depending upon the size and structural details of a particular device, it is only necessary that the accumulator be constructed in such a way that the inner set of convolutions can act in an essentially friction-free, independent manner, while the rotary table on which the outer set of convolutions is supported acts to advance the convolutions in a circular path on the table. The only other essential requirements is that no obstruction be presented to the free movement of the reverse bend.
The initial diameter of the outer set of convolutions, i.e., the inner most convolution in the outer set, is determined by the relationship between pinch roll and table rotation speeds. For example, if the pinch rolls are driving the input strip at X feet per minute and the table is rotating at r rpm, the approximate diameter of the initial convolution in the outer set will be: EQU Convolution Diameter=X=r.pi.
and this will be true regardless of the table diameter, assuming of course that the table diameter is at least as large as the diameter of the convolution. This equation will not give an exact value: in most cases, the actual is diameter will be slightly larger than that predicted for two reasons. First, the strip stiffness will produce a spring effect with the free bend and tend to push the initial convolution outwards. Second, centrifugal force will tend to enlarge the diameter. In addition, the initial diameter of the free bend interconnecting the inner end outer sets of convolutions will be the difference in the radius of the initial convolution in the outer set and that of the inner arbor. As the speed of rotation of the table increases relative to the feeding speed of the incoming strip, the diameter of the convolution being formed will decrease, whereas if the speed of rotation of the table decreases relative to strip feeding speed, the diameter of the resultant convolution will increase. It is thus possible to correlate feeding speed and rotational speed of the supporting table to provide an initial outer convolution of the desired diameter. Since the diameter of the initial convolution may be readily controlled, an outer roll cage is not required to maintain the strip on the table since it will automatically assume the desired diameter in accordance with the foregoing formula.
As a practical matter, however, it is preferred to provide a series of guide rollers surrounding the rotatable table as a precautionary matter and to keep the strip on the table while the first convolution is being established. However, such rolls or other guiding means may be of relatively light construction and may be retracted or removed once the initial convolution has been established.